This invention relates to an automatic hot drink maker installed on a floor or counter in a store such as a food service shop and a restaurant, and more particularly, to an automatic coffee urn in which a brewed coffee storage tank is located independently of a hot water tank and is heat-conditioned to maintain a predetermined temperature suitable for drinking coffee.
Various types of hot drink makers have been proposed and one of them is of the type in which hot drink such as coffee or soup is prepared by pouring hot water onto powdered or ground material in a funnel member and stored in a hot drink storage tank to obtain prepared hot drink at any desired time.
An automatic coffee urn which is one example of a hot drink maker of the type described above will be described hereunder in conjunction with FIG. 1.
Referring to FIG. 1, an automatic coffee urn comprising a vertical casing 50 made of such as stainless steel in which a hot water tank 2 is located at the bottom of the casing 50 and the side and bottom walls of the tank 2 are surrounded by a heat-insulating material 3. A coffee storage tank 4 is suspended in the hot water tank 2 such that the upper end portion of the tank 4 extends horizontally and the outer edge of the upper end portion is attached to the upper end of the side wall of the tank 2 so as to constitute an upper cover of the hot water tank 2. A coffee funnel 5 in which a filter element 5c is provided and ground coffee 6 is loaded is detachably attached to an opening 25 formed on the front wall of the casing 50 just above a lid 4a fitted to the coffee storage tank 4 so that a flow out opening 5a opens just above an inlet hole provided for the lid 4a. The level of the hot water W in the tank 2 is detected by a water level detector 11 and an electromagnetic water supply valve 14 is operatively connected to the level detector 11 and controlled by a signal from the detector 11 to supply water into the tank 2 and always maintain a necessary amount of hot water W in the tank 2. The hot water W is heated by an electric heater 13 disposed in the low portion of the tank 2 and a temperature of the hot water W is suitably controlled by a thermostat 12 electrically connected to the heater 13. A pipe 8 has one end extending in the hot water W from the upper portion of the tank 2 and the other end provided with a spray head 7 which is positioned above the funnel 5 to spray the hot water W in the tank 2 onto the ground coffee powder loaded in the funnel 5 by the operation of a pump 9 incorporated in the pipe 8. The brewed coffee drink is fed through the flow-out opening 5a into the storage tank 4 and the coffee thus prepared and stored in the storage tank 4 is taken out as occasion demands by handling a cock 1 through an outlet pipe 4b connected to the bottom of the storage tank 4.
Regarding the automatic coffee urn of the type described above, the hot water W in the tank 2 will be maintained at 93.degree.-97.degree. C. which is deemed to be a temperature suitable for brewing coffee and the temperature of the brewed coffee C in the storage tank 4, which is suspended in the hot water tank 2, is also maintained at substantially 93.degree.-97.degree. C., which is considerably high temperature for the coffee to be drunk. Thus, the high temperature such as 93.degree.-97.degree. C. will make flavor of coffee disperse easily and degrade its quality and taste because a temperature suitable for drinking coffee is generally considered to be about 85.degree. C. Therefore, it is undesirable to locate the coffee tank 4 in the hot water W having a high temperature of 93.degree.-97.degree. C. for a long time. In order to prevent the direct contact of the tank 4 with the hot water W, although a heat insulating jacket member 26 may be provided to surround the coffee tank 4 to form an air space therebetween, influence of the temperature of the hot water W upon the coffee C cannot be completely avoided even though the jacket 26 is arranged. In addition, as the cock 1 is usually positioned outside the casing 50 in the air, temperature of a first cup of coffee after a no-use long period is low in comparison with that of the coffee C in the tank 4 because at first heat of the coffee C is spent for warming the cock 1 and the temperature of the succeeding cup of coffee would be again about 93.degree.-97.degree. C. Thus, cups of coffee having uniform and desirable temperature cannot be obtained through the cock 1. Moreover, it is impossible to adjust the temperature of prepared hot drink in the storage tank so as to be suitable for kinds of drinks.
When a certain amount of hot water W has been spent on for brewing coffee and taking out of several cups of coffee and the water level in the tank 2 lowers, the level detector 11 operates to control the electromagnetic water supply valve 14 so as to supply water into a bottom portion of the tank 2 from a water source such as water service through a pipe 27 connected thereto. Since the supplied water is cold, it will stay at the bottom portion of the tank 2 and cool the coffee tank 4 if the bottom thereof is positioned at a relatively low position. In order to obviate this advantage, it is required to locate the coffee tank 4 at a relatively high level in the tank 4, which fact makes the volume of the tank 2 enlarge and requires much time to heat up the water in the tank to a predetermined temperature. Moreover, the manufacture of a large tank will bring about constructional problem such as welding work and require much time and expense for the manufacture.
In order to obviate the defects of the automatic coffee urn of the type described above, is provided an automatic coffee urn in which a coffee storage tank is located in a casing independently of a hot water tank, for example, as described in U.S. Pat. No. 3,149,556 to James S. Martin. In James, a coffee storage tank is located independently of a hot water tank and heated by a heater disposed only at the bottom of the storage tank. However, since the storage tank is heated only from the bottom, the whole wall structure of the storage tank is not uniformly heated and temperature difference exists at upper and lower portions thereof, i.e., the brewed coffee in the storage tank. Therefore, the coffee having a constant temperature cannot be obtained successively.